ww: lib tests run via -T test mode; bare mains retired (closes @test conversion)

'ww test' gains the istest build path (-T injection in build_one/
buildone) and do_test/dotest accept -I, mirroring do_run - both twins.
The 35 converted lib tests drop their interim bare mains (-T
synthesizes the entry from @test fns and rejects a user main); their
35 C run-drivers flip 'ww run' -> 'ww test'; 989_lib_byteid compiles
lib tests under -T (8 user-main probe fixtures stay non-T, gated on
the fixture field). Abort-on-first-failure stands until the deferred
record-and-continue harness lands with the multi-package arc.

lib/regex/regex_test.ww

@@ -2568,55 +2568,3 @@ type prrow = struct {
 		i += 1;
 	};
 };
-
-export fn main() i32 = {
-	lit_and_match();
-	size_aliases_distinct();
-	void_aliases_distinct();
-	charset_payload();
-	repeat_payload();
-	struct_shapes_and_finish();
-	compile_literal_program();
-	compile_any_program();
-	compile_empty_program();
-	thread_shape();
-	newmatch_discriminates();
-	result_free_noop();
-	strerror_identity();
-	is_consuming_kinds();
-	delete_thread_middle();
-	add_thread_dedup_inherit();
-	run_thread_literal_program();
-	run_thread_anchored_route();
-	search_matches();
-	search_early_exit();
-	search_no_match();
-	test_matches();
-	find_cases();
-	findall_content();
-	findall_fields();
-	fold3_programs();
-	fold3_compile_errors();
-	find_last_groupstart_cases();
-	shift_direct();
-	fold3_find_cases();
-	fold4_programs();
-	fold4_charsets();
-	fold4_compile_errors();
-	fold4_find_cases();
-	fold4_findall();
-	add_thread_dup_independence();
-	fold5_compile_errors();
-	run_thread_group_arms();
-	fold5_find_cases();
-	fold5_optional_group();
-	fold5_submatches();
-	parse_repetition_cases();
-	fold5b_compile_errors();
-	fold5b_find_cases();
-	fold5b_findall();
-	fold6_compile_errors();
-	fold6_charsets();
-	fold6_find_cases();
-	return 0;
-};